It’s just a drill, so don’t be alarmed if you see sailors in battle gear taking up fighting positions around local Navy bases this week.

Installations in the continental United States, Guam and Hawaii will participate in Exercise Solid Curtain-Citadel Shield today through Friday, giving officials a snapshot of military readiness as the 10th anniversary of the Sept. 11 attacks approaches.

The Navy plans to simulate real-world threats, incorporating lessons learned from the 2000 bombing of the Navy destroyer Cole and the 2009 Fort Hood shooting, among others.

“There will be a variety of scenarios through that week,” said Brian O’Rourke, a Navy spokesman. He wouldn’t detail the scenarios so as not to tip off the forces taking part in the exercise.

For most people the exercise will make it harder at times to get on and off naval bases.

“There may be a little bit of traffic now and then immediately around some of the bases during the week,” he said.

Civilian boaters in the San Diego Bay will not be affected, he said.

Nationwide, the exercise will replicate a variety of possible scenarios, from an explosive going off on a Navy base to a bomb threat at a recruiting center. The public may see people in battle gear with guns, military dogs and fixed fighting positions manned at some bases.

Security officials will track scores of potential threats and sailors’ responses to them from a control room at Norfolk Naval Station in Virginia.

“You want to train the way you fight, so if you don’t make it real you’re not getting the full training that you not only should get, you have to get out of it,” said Capt. Sam McCormick, U.S. Fleet Forces director for fleet anti-terrorism.

Army and Marine Corps officials also will observe the exercise, which is being coordinated by U.S. Fleet Forces Command.

The Navy said the annual exercise involving more than 250 scenarios isn’t a response to a specific threat but helps identify where forces are vulnerable. A review last year found that some things could be improved, McCormick said.

“You have ships personnel trying to coordinate with security personnel on the shore that we found, quite frankly, we could do it a little better,” he said.

The drill will also involve local and federal agencies including the FBI, San Diego and harbor police, the city’s Office of Homeland Security, the county’s Office of Emergency Services, the Port of San Diego and the Red Cross.